Well, the result of a successful feint is to deny the target his Dex bonus. Unless you have a special attack form that can take advantage of this, or the enemy has a surprisingly large Dex bonus, this is generally a big "so what". However, for rogues and others with sneak attack (or similar ability), it is very useful.
Every character class that has sneak attack also has the Bluff skill as a class skill. In other words, allowing BAB to help in making a sneak attack only really benefits those classes that don't really benefit all that much from feint attacks anyway.